World-wide attention has been directed toward defining and seeking solutions to the problem of protein deficient diets among large portions of the world's population. Many studies, taking into consideration expansion rates, have concluded the world is running out of food. The upward trend in world population and increasing cost of traditional animal food proteins has provided strong incentives for utilization of oilseed proteins directly in human diets. Acceptability of oilseed protein products in terms of their functional properties in food systems and nutritional value will largely determine the extent of their utilization by the food industry.
Cottonseed is one of the principal oilseeds of the world and in recent decades has been studied as a possible source of food protein. The development of a process to remove its gossypol-containing pigment glands (Gardner et al., U.S. Pat. No. 3,972,861) and the genetic development of a variety of "glandless" cottonseed (GLCS) has provided a raw material capable of use in foods. Processes have been developed to produce flours, concentrates, and isolates. GLCS kernels are currently available commercially; however, the development of a market for products incorporating this edible oilseed has not been achieved. Investigators at the Food Protein Research and Development Center at Texas A&M University have already tested the utility of cottonseed products in several food applications (Cater et al., 1977; Lawhon, J. T., Cater, C. M. and Mattil, K. F. 1970 "Preparation of a high-protein low-cost nut-like food product from glandless cottonseed kernels" Food Technol. 24:77; Lawhon, J. T., Cater, C. M., and Mattil, K. F. 1972a "A whippable extract from glandless cottonseed flour" J. Food Sci. 37:317; Lawhon, J. T., Rooney, L. W., Cater, C. M., and Mattil, K. F. 1972b "Evaluation of a protein concentrate produced from glandless cottonseed flour by wet extraction process" J. Food Sci. 37:778; Lawhon, J. T., Cater, C. M. and Mattil, K. F. 1975 "Sensory, analytical evaluation of cake doughnut fortified with protein from oilseed flours" Food Prod. Dev. 9:110; Lawhon, J. T., Cater, C. M. and Mattil, K. F. 1977 "Evaluation of the food use potential of sixteen varieties of cottonseed" J. Am. Oil Chemists' Soc. 54:75; Green, J. R., Lawhon, J. T., Cater, C. M. and Mattil, K. F. 1976 "Protein fortification of corn tortillas with oilseed flours" J. Food Sci. 41:656; Green, J. R. Lawhon, J. T., Cater, C. M., and Mattil, K. F. 1977 "Utilization of whole undefatted glandless cottonseed kernels and soybeans to protein-fortify corn tortillas" J. Food Sci. 42:790). One such product, "Tamunuts", has been developed by roasting the glandless kernels. Roasted kernels have been used in various foods as a nut replacement. In experimental cookery, GLCS flour, concentrates, and isolates have also been successfully integrated into food systems; however, these latter products are not presently available on a commercial basis.
Curd-like products such as tofu have long been prepared from soybeans. Traditional Chinese curd is prepared in the following manner; whole soybeans are soaked overnight in tap water. The soaked soybeans are blended with water and the mixture filtered through a linen cloth. The soybean milk is then steamed for 30 minutes or brought to boiling and heated at that temperature for 5 minutes, cooled to about 70.degree. C. or 50.degree. C. and precipitated with calcium sulphate. When the curd forms, it is cut into cubes with a knife to facilitate the release of whey. The curd is then gently pressed overnight. Variations of this procedure occur after preparation of the soybean milk to yield different textures of the final tofu product, for example, cotton grade tofu or silk tofu, based on percentage of calcium sulphate added. The tofu has also been frozen and another process produces an instant dried powder. Various processes for the preparation of soybean tofu and its incorporation into food systems is detailed by Shurtleff, W. and Aoyagi, A. 1975: "The Book of Tofu: Food for Mankind". Autumn Press, Inc., Mass.
Another process has been developed by Schroder, D. J. and Jackson, H. 1972 "Preparation and evaluation of soybean curd with reduced beany flavor" J. Food Sci. 37:450, in which a soybean curd is produced with reduced beany flavor. In their process, whole soybeans were quickly rinsed in cold water and placed in a 1-gal blender together with boiling water. The ratio of water to beans was 9:1 and the temperature of the water between 85.degree.-95.degree. C. The beans and water were then blended at full speed for 3 minutes. The resulting suspension was held at approximately 100.degree. C. for 30 minutes by injection of live steam. After the steam treatment, the suspension was filtered through muslin bags to yield two fractions--a soybean milk and residue. The milk was maintained at 80.degree. C. and the curd precipitated by the addition of 0.2% calcium sulphate. The curd was allowed to stand a further 30 minutes, the temperature being approximately 80.degree. C. throughout. The curd was placed in small cheese hoops and allowed to drain freely for a short time, after which it was pressed overnight at a pressure of approximately 1 psi.
Microstructure analyses of soybean protein aggregates or curd has found that heat denaturation of the protein was necessary in forming the network structure of the aggregates (Lee, C. H. and Rha, C. 1978 "Microstructure of soybean protein aggregates and its relation to the physical and textural properties of the curd" J. Food Sci. 43:79). The three dimensional network structure of the aggregate derived from heated soybean protein showed a low sedimentation rate, high curd yield, high water-holding capacity, low value of hardness and high springiness compared to the unheated precipitates of globular structure.